18 th Dec 2004 Capacitors Application Edward Chen.
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Transcript of 18 th Dec 2004 Capacitors Application Edward Chen.
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18th Dec 2004
Capacitors ApplicationEdward ChenCapacitors ApplicationEdward Chen
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18th Dec 2004
Electrode Plates Dielectric
The value of a capacitor is measured in farads. For 1 farad of capacitance, 1 coulomb of charge is stored on the plates,
when 1 volt of force is applied.
1 farad = 1 coulomb / 1 volt
1 coulomb represents ~ 6 x 1019 electrons
All capacitors utilize the same basic mechanism in their structureAll capacitors utilize the same basic mechanism in their structure
2
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18th Dec 2004
ESL - Inductive Reactance (XL)
opposes Capacitive Reactance
XZ
ESR
XC
XL
X
0
Impedance is now a factor of resultant
Z = (XC-X
L) + ESR
2 2
3
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18th Dec 2004
Loss Factors in Capacitors
Based on Vector relationshipDF = cot(Theta) = ESR / XC
PF = cos(Theta) = ESR / ZQ = tan(Theta) = XC / ESR = 1 / DF
whereDF = Dissipation FactorPF = Power Factor Q = "Q" or figure of merit
Theta
XC
Z
ESR
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18th Dec 2004
Self-Resonance
Rea
ctan
ce
Frequency
XC decreasing
The frequency at which XC = XL is the self-resonant frequency.
At this frequency, XC=-XL, or zero, and the impedance is equal to the ESR.
Prior to this frequency, component behaves as capacitor; after this frequency, component behaves as inductor.
XL increasing
self-resonant frequency.
LC2
1F
5
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18th Dec 2004
Capacitor ApplicationCapacitor Application
•Decoupling•Coupling•Filtering•Timing/Wave-shaping
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18th Dec 2004
DecouplingDecoupling
PowerSupply
Load(ex.IC)Vin Vout
Vin Vout
Function: Absorb the voltage change (noise).Suitable Cap: Tan Cap, KO Cap, MLCC, Al E Cap
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18th Dec 2004
CouplingCoupling
Function: Remove the DC voltage of A circuit and Transmit the exchange voltage to B circuit. (Allow an AC signal
pass, but stop DC.)
Suitable Capacitors: Tan Cap, MLCCEx. Horn.
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18th Dec 2004
FilteringFiltering
Function:• Rectified AC smoothing• Frequency selective filteringSuitable Cap: KO, Tan Cap, Hi C/V MLCC, Al E Cap
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18th Dec 2004
Timing / Wave-shapingTiming / Wave-shaping
Function: Timer Circuit (RC Timer).Suitable Cap: MLCC, KO Cap.